33 
Dimensions. — The specimen described in all probability was not found 
in situ ; the test is silicified, and several small pieces of white limestone adhere 
to it ; the interior of the mouth is covered with crystals of calcite. It comes 
from the Yass District. 
Genus — BELLEROPHON, Montfort. 
Bellerophon Jukesii, L. G. de Koninch. 
PI. IV, Pig. 2. 
Shell of medium size, suhdiscoid, faintly umhilicate ; whorls of the 
spire increasing rapidly in size, and ending in a mouth that is higher than 
broad ; there is a well-marked carina on the hack, produced by the hand of 
the sinus. Surface ornament with faintly-marked lines of growth almost 
invisible to the naked eye. 
Dimensions . — Diameter, thirty; width of the last whorl, fifteen; height 
of the same, eleven millimetres. 
Delations and Differences . — In profile this species has some resem- 
blance to D. IVenlockensis, Sowerhy, in which the whorls envelope one 
another to the same extent, and the carina is similar, hut Avhile the English 
species is globose the Australian is suhdiscoidal, and is relatively larger. 
Horizon and Locality . — One slightly distorted specimen was found in 
a soft yellowish-brown argillaceous rock at Ptock Elat Creek. This rock is 
similar to the matrix of the Silurian Trilohites from the same place. I have 
dedicated this species to J. B. Jukes, who has been removed too soon from 
Science and the high estimation of his many friends. 
